Production of hydrogen from hydrocarbons



July 28, 1953 s. P. ROBINSON PRODUCTION OF HYDROGEN FROM HYDROCARBONS Filed April 15, 1,946

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INVENTOR. S. P. ROBINSON 1;Y 244 3 ATTORNEYS Patented July 28, 1953 PRODUGTION OF HYDROGEN FROM HYDROCARBONS Sam P. Robinson, Barflesville, Okla., assignor to Phillips Petroleum Company, a. corporation of Delaware Application April 15, 1946, Serial N0. 662,149

15 Claims. (C1. 23-212) This invention pertains to the production o! hydrogen by cracking of hydrocarbons at elevated temperatures. In a specific ernbodiment che invention relates to a process for cracking hydrocarbons 110 produce hydrogen utilizing metal- 1ic pebbles as combined catalyst and heat exchange material for the reaction.

Cracking of hydrocarbons such as natural gas and vaporized heavier hydrocarbons is common- 1y effected by heating these gases 110 high temperatures either With or without the aid of cat; alysts. Since the cracking process is endothermic in natura, both the sensible heat and heat of reaction must be supplied to the ga.s being cracked. An efiective method of cracking is afforcled by pebble heater type operation which entails supplying all of the heat requirements in the cracking zone by means of a. stream cf hob refractory pebbles, the pebbles having been beated, usually, by fuel gas combustion in a separate heating zone. It is of course desirable to utilize a pebble which is highly refractory, is strongly catalytic, und which des not lose its catalytic activity under the normally severe conditions existing in the pebble heater, itself.

It is an object of this invention to provide a process for cracking hydrocarbons 130 produce hydrogen which eflectively utilizes a moving-type combination catalyst and heat-exchange material.

It is also an object of the invention to provide a process for producing hydrogen and carbon as a by-product, using the pebble heater method, in which catalytic activity is not seriously diminished during the heating cf the pebbles.

A further object; of the invention is 1:0 provlde a method of heating metallic pebbles in pebble heater-type processes without substantialbxidal tion, and deterioration cf the pebbles;

Other objects of the invention will become ap-' parent from the accompanying description.

Conventional pebble heater apparatus provides a, pebble heating chamber positioned above a reaction chamber with a connecting neck between the two chambers for gravity flow of pebbles from the u"pper to the 1ower chamber. Pebbles o! ceramic, metal, 01 other refractory material are heated by direct contact with hot combustion gas as they fiow thru the pebble heater. They then pass thru the neck between the chambers and into the reaction chamber where they give up heat to the reactant gases which are usually passed therethru in countercurrent flow to the downwardly flowing pebbles. 011 emerging from the reactor, the pebbles are considerably cooler thzin reaction temperature, so they are transferred by elevator to a 1evel above the inlet 120 the pebble heater ancl are permitted to fiow back into the heater for reheating and continuance of the operation cyc1e.

The term pebble as used herein refers to a refractory material in flowable form and size which will fiow readily by gravity thru the chambers cf a pebble heater-type apparatus. Pebbles are preferably substantially spherical and vary in size from about /8" 130 1" in diameter With the preferred size about AI to /g".

The present invention utilizes metallic pebbles seleeted for their relatively high catalytic aetivity and provides pebble heating techniques which prevent substantial oxidation at high temperatures. It is foi1nd that when utilizing iron, nickel, Inconel, and Monel pebbles, heating canditions can be established in the heater which permit the required ranid high te'mperatu-re hea.ting of the pebbles by direet contact with combustion gas without the usual oxidation of the metal and consequent impairment of its eatalytic activity and high erosion thereof from circulation thru the system. These metals are strongly catalytic in effecting complete cracking of hydrocarbons and are very desirable in the proc ess cf the invention for this reason.

Inconel, the preferred metallic material for use in the process of the invention, has the following composition by weigho: nickel, not less than chromium, 11-15%; manganese, not over 1%; iron, not over 10%; silicon, not over 0.5%; earbon, not over 0.15%. 'I'he conventiona1 composition is nickel, 15% chromium, and

5% iron.

Monel, an excellent alloy for the process, has

the following composition by weight: nickel, 63-- 70%ymanganese not over 2%; iron, not over 2.5%; silicon, not over 0.5%; carbon, not over 0.5%; aluminum, not over 0.5%; copper, balance.

A conventional composition of Monel is nicke1, 67%; copper, 30%; manganese, 1%; iron, 1.4%; silicon, 0.1%; carbon, 0.15%.

Both nickel and iron pebbles also function effectively in the process of the invention. Where enough to avoid entrainment in the gases coutacted.

While the invention is widely applicable 1:0

in avoiding any slight oxidation of the pebbles. It is important to avoid. introducing more oxygen than is stoichiometrically required I:o completely oxidize all of the C and I-I in the heating zone either when adding steam to the fue1 or when no steam is added.

- Economyof o peiation and higher efificiency are obtained in the prcess of the invention by utiliz- Ing heat exchange between Ehe flue gas from the hydrocarbon feed such as natural 'gas, which is preferably preheated, is fed into the reaction chamber of a pebble heater in countercurrenb relation to a downwardly flowing stream of hob A Inconel pebbles. The pebbles must be sufiiciently hob to maintain a cracking temperature of be-.

tween about 1300 and 2000 F. T0 maintain these cracking temperatures under the very short reaction times vvhich may' be used, requires pebble-temperatures of from about 1500 130 2400"- F.;pebb1e temperature varying with reactiontime and pebble flow rate. Reaction times of about 0.05 130 0.2 second are sufficient when operating at the above temperatures and with the metallic pebbles disclosed herein. 'Ihe pebbles emerging frozn the reactor are considerably cooled, varying in temperature from about 500 1301000 F. and are transfe rred by elevator to a point above the pebble heating chamber from which they fiow by gravity into seid chamber.

The elevator may be ofthe bucket, screw, or gas 1ift type, however, a, bugket elevator offe1's more efiicient operation in the process than either of the other types anal is preferred.

Pebbles entering the heating chamber am contacted with a stream of hot combustion gas pro:- duced in a burning chamber acljacent-the heater. In order t0 prevent oxidation of the metallic pebbles at the high temperatures involved (temperatures up to about2800" F.) the invention provides for maintaining a mild1y reducing-atmosphere in the pebble heating chamber. In cases where there is a small accumulation of carbon on the pebbles from deposition in the reaction zone, this reducing action ean be obtained by passing a small quantity of steam into the heating chamber along With the heating gas. 'Ihis steam addition effects the water gas reaction With the hot carbon on the pebbles to produce H2 and CO and maintain reducing conditions when little or no -When the feed and operating conditions in the rea)ction zone a1e not conducive I;o the deposition heat ing ohamber and the fuel fed thereto, as we11 as between I;he :filuents from the reaction chember and the feed thereto. 'Ihe use of small-tube, high-velocity heat exchangers prevents carbon deposition in the exchangers.

In order to present a more complete description of the inventio n reference is made 110 the drawing which is a diagrammatic illustration of one arrangement of apparatus for performing the insurplus oxygen is present in the combustion gas.

vention. In operation heat is supplied for the process by heating pebbles Iin heater EI.. Any

desirable hydrocarbon fue1 from line I2 is burned 1 in bustle ring or burner I8, WiI;h tl1e aid of air admitted thru line I I. Steam may be mixed with the fue1 or air as desired 110 efiect tne removal of any residual carbon on ehe pebbles anti to he1p in preventing pebble oxidation. The air 01' oxygen input is c1osely regulated to assure incomplete combustion of the fuel admitted thru line I2. Hot combustion gas of a reducing nature passes thru hea.ter II, raising the temperature of the pebbles to the desired degree, and passes 011 via bustle ring I5, 1ine I5, and heat-exchanger II out 0I' the systern to any desired point 02 use 01 disposal. Fuel in line I2 ispreheated in exchanger II. I-Iot pebbles continuously pass into neck I8 and reaction chamber I9 frorn heater II. These bot, fiuent, metallic pebbles are contacted in reactor I9 by the preheated gaseous hydrocarbons to be cracked which are admitted thru line 2I,

heat-exchanger 22 and bustle ring 23. In pass ing thru reactor I9 the hydrocarbon gases are heated to cracking temperatures and thru the catalytic action of themetallic pebbles are rapidly cracked to hydrogen and carbon, most of I:he

latter being entrained in the effluent gases which pa ss via. bustle ring 2IJ, line 24, and heatexchanger 22 to product separation means 25. Means 25 separates the various constituents such as hydrogen, which is removed thru line 26, carbon thru 1ine 2'I, ar 1d residualeonstituents thru line 28. When desired effluents from the reaction may be recycled thru line 29 and valve 3I to feed 1i1'1e 2 I. It is also feasible 120 recycle any residual hydrocarbons from separation means 25 via 1ine 3200ntr011ed by va1ve 33 to feed line 2 I.

.Flowof pebbles thru heater II and reactor I9 is regulated by feeder 34 in conduit 35 in such manner as required to properly heat Ishe pebbles in heater II and the gases in reactor I9. In this tion of supplied oxygen to the oxygen required for complete combustion should cf course be relatively close 110 unity in order to economize on fue1. In many areas the cost cf natural gas '1s so 10W that economy of fue1. is secondary to assurance of a reducing atmosphere and no great care need be exercised in obtainin the utmost heat from the fue1. In some cases it is desirable 130 uti1ize a portion of the efiluents from the reaction chamber to supplement the fue1 burned to generate combustion gas for heating Ehe pebbles since this expedient aids in mai ntaining reducing conditions in the heater. Ihe addition of a relatively small amount o1 steam even when there is no carbon deposited 011 the 'pebbles appears to aicl manner of operation, the system is full of pebbles from the upper portion of bester I I to I;he pebble feeder 34 so as to maintaina compaet mass o1 stream of pebbles I0 in the chambers and conneoting throat. 'Ihis facilitates the avoidance of mixing combustion gas with hydrocarbon gases from reactor I9 by Way of throat I8. Feeder 34 and conduit 35 pass pebbles into elevator 36 which elevates them and discharges them into conduit 3'I for gravity fiow back into heater I i where they slightly above atmospheric such as 3 pounds per sqnare inchgage or less, but other pressures With- 'iIi rxasonable limits my be used. Maintaining substantially eq'ual pressur6s in the heater and the reac'cor ab all times tends 150 eIiminate fiow of gzases from chamber 60 chamber. When raqu=ired, steam may be admioted thru lines 38, 30;. and I 150 block the flow f gases thru conduits 37, I8, and= 35, respestivel'y.

When operati'ng withnatural gas as feed and as fuel, and with %1" InconeI peb=bles, under the following condition-s a reeovery 0f approximately 92% of the feed hyd-rogen is efl'ected with no 0bservable oxidation of the pebbles.

Cracking temperature --F-- 1850 Pebble temperature: entering reactar F.- 2200 Pebble temperature leaving reactor ---F-- 1100- Feed temperature (preheat) --F-- 950 Pressure of efiluent product gas (lbs. gauge) 1.5 Reaction time in second5 0.08

Pebble temperature entering heater F 1050 Gas temperature in heate F 2500 Fuel temperature (.preheat) F 800 Mole ratio of fue1 to steam 1/0.2 Mole ratio of oxygen to fue1 1.9/1 Pressure of efliuent flue ga-s (lbs. gauge) 1.5

Numerous advantages accru.e from operation according 110 the invention. The use of highly catalytic metallic pebbles without concomitant oxidation thereof permifis Ehe use of very short reaction times at not unusuall3i high temperatures. The metallic pebbles disclosed are indestructible and have an indefinite catalytic anal heat exchange l-ife and effect a considerable economy over ceramic pebbles over an extendecl period. Avoidance of oxidation of the pebbles not on1y materially extends their life but also assists in maintaining high production rate in the prosess. By preheating the feed and the fuel to relatively high temperatures, uti1izing sensible heat cf the efiiuents from the reaction and heating zones, much lower pebble temperatures and beating zone temperatures are feasible. This preheating of fuel and feed also permits closer temperature control in both chambers and contributes to efficiency of operation.

The various modifications described provide for rather flexible operation 1:0 meet the varied conditions required in diiferent processes. It Will be understood that certain features and sub-combinations may be desirable alt-hough not specifically described. 'I'his is contemplated by and is within the scope of the claims. I1: is also obvi0us that certain changes in details within the scope of the claims may be made without departing from the spirit of this invention. I1; is therefore to be understood that my invention is not 150 be unduly or unnecessarily limited to the specific details described and shown.

I claim:

1. A continuous process for producing hydrogen Which comprises continuously passing a hydrocarb0n gas thru a reaction zone in contact with a compact countercurrent stream of hob pebbles essentially constituted of ab least one metallic material of the dass consisting of iron, nickel, chromium, and copper and ab such a temperature that said gas is substantially cracked to hydrogen and carbon, transferring said pebbles from said reaction zone 170 a heating zone, reheating said pebbles to above cracking temperature by contacting them in said heating zone With a countercurrent stream of water gas and hob blue gas devoid of free oxygen, whereby substantial oxidation of said pebbles is avoided, transferring said pebbles to said reaction zone to. domplete a cycle 0f operatiomancl reaoverins the hydrogen produced.

2. Process of clai;m 1 in which the cmckirig.

time is between about .05 am! 0.2 senond 3, Prozess of c1aim 1 in which thecrackin&

temperature is between about 130.0 and 200.0 F.

4. Process oi claim 1 in which .the pebblfls are constituted cf nickel.

5'. Process of claim 1 in which the pebbles am constituted of. nickel-chromium-iron.

6 Process cf claim 1 in which. the pebbles are constituted 015 nickel-copper.

perature cf between about 1300 and 2000 E;

and substantially cracked to hydrogen, and ca;r bon thereby depositing carbon on said pehble's withdrawing said pebbles from said reaction. zone and transferring them 130 a pebb1e heating= zone,

introducing to said pebble heating zone a stream: of hot b1ue ga.s devoid cf free oxygen am! steamu proportioned so as to remove substantially alt of said carbon from said pebbles and maintain a mildly reducing efiect on said pebbles whiler heating them to a temperature of between aboutr 1500 and 2400 F., returningsaid pehbles. v said reaction zone to complete the cyc1e,

recovering t;he desired productszr 8. In a catalyticchemical confversion pmcessw wherein heat required for the conversion is; sup

p1ied to a reaction zone by circulating a, compact stream of hot metallic pebbles thru said reaction zone in contact with a stream cf gaS to be converted and said pebbles are then transferred a heating zone and contacted with a heating gas comprising hot b1ue gas and again circulated thru said reaction zone, the step 01 controlling the character of the heating gas tc' maintain a reducing eflect with respect; to said metallic pebbles in said heating zone by utilizing a blue gas devoid of free oxygen and admixed with steam. 1

9. 'I'he process of claim 8 further characterized in that said reducing efiect is maintained by on1y partial combustion of a fue1 to produce an incompletely oxidized gas high in carbon monoxide content which is then used as said blue gas.

10. In a catalytic hydrocarbon conversion process wherein heat required 'for the conversion is supplied to a conversion zone by circulating a compact stream of hot catalytic metallic pebbles thru said conversion zone in contact with a stream of hydrocarbon gas to be converted under conditions effecting said conversion and depositing a substantial amount of carbon 0n said pebbles, and wherein said pebbles are thei1 circulated thru a heating zone to be reheated and are then recirculated thru said conversion zone, the step which comprises supplying to said heating zone a stream of hot blue gas containing substantially no free oxygen and sufficient water vapor react with said deposited c2rbon to form water gas whereby a reducing effect with respect to said metallic pebb1es is maintained in said heating zone.

11. A continuous process for the catalytic conversion of hydrocarbons which comprises continuously gravitating a unitary, compact, fluent mass of to 1" metallic pebbles constitutsd at least one member -of the group consisting 01 iron, nickel, chromium, and coppei* through a anal seris 017 vertically extending zones ccimprising a pebble heating zone, a reaction zone positioned at a lower level than said heating zone, and a relatively narrow interconnecting zone; contimidusly contacting that section of said mass of pebbles flowing through said heating zone with a stream 015 bot b1ue gas free of uncombined oxygen and non-oxidi'zing with respect 130 said pebbles under the conditions in said heat- :lng zone so a5 130 heat said pebbles to a temperature in the range of 1500 to 2400 F. without substantial oxidation thereof; continuously coutacting that section of said mass of pebbles flowing through said reaction zone with a stream of gaseous hydrocarbon so as 150 effect the desired conversion thereof with concomitant cooling of the pebbles; maintaining substantially the Same gas pressure in the heating anal in the reaction zones; returning the cooled pebbles 130 said beat- 1ng 'zone; and recovering an effluent from said reaction zone.

12. A continuous process for the catalytic comversion of hydrocarbons which comprises coutinuously gravitating a unitary. compact, fluent mass 0f /8" to 1" metallic pebbles through a series of vertically extending zones comprising a pebble heating zone, a reaction zone positioned at a lower leve1 than said heating zone, and a relatlvely narrow interconnecting zone; coutinuously contacting that section of said mass o1 pebbles fiowing through said heating zone with a; stream of bot; fiue gas free of uncombined oxygenand non-oxidizing with respect to said pebbles under the conditions in said heating zone so as to heat said pebbles to a temperature in the range of 1500 to 2400 F. without substantial oxidation thereof; continuously contacting that section cf said mass 015 pebbles fiowing through said reaction zone with a stream of gaseous hydrocarbon so as efl5ect the desired conversion thereof with concomitant cooling o! the pebbles; returning the cooled pebbles to sa1d heating zone; and recovering an eflluent from said reaction zone.

13. The process of c1aim 12 utilizing Incone1 pebbles.

14. The process 01 claim 12 utilizing Mone1 pebbles.

15. The process 015 claim 12 utilizing iron pebbles.

SAM P. ROBINSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2367928 Clark Jan. 23, 1945 2389636 Ramseyer Nov. 27, 1945 2443,337 Weber June 15, 1948 2471,104 Gohr May 24, 1949 OTHER REFERENCES Fue1 Flue Gases, published by American Gas Association, 1940, page 159.

Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry, 1922, Longmans, Green and Co., New York, vol. I, page 280. 

1. A CONTINUOUS PROCESS FOR PRODUCING HYDROGEN WHICH COMPRISES CONTINUOUSLY PASSING A HYDROCARBON GAS THRU A REACTION ZONE IN CONTACT WITH A COMPACT COUNTERCURRENT STREAM OF HOT PEBBLES ESSENTIALLY CONSTITUTED OF AT LEAST ONE METALLIC MATERIAL OF THE CLASS CONSISTING OF IRON, NICKEL, CHROMIUM, AND COPPER AND AT SUCH A TEMPERATURE THAT SAID GAS IS SUBSTANTIALLY CRACKED TO HYDROGEN AND CARBON, TRANSFERRING SAID PEBBLES FROM SAID REACTION ZONE TO A HEATING ZONE, REHEATING SAID PEBBLES TO ABOVE CRACKING TEMPERATURE BY CONTACTING THEM IN SAID HEATING ZONE WITH A COUNTERCURRENT STREAM OF WATER GAS AND HOT BLUE GAS DEVOID OF FREE OXYGEN, WHEREBY SUBSTANTIAL OXIDATION OF SAID PEBBLES IS AVOIDED, TRANSFERRING SAID PEBBLES TO SAID REACTION ZONE TO COMPLETE A CYCLE OF OPERATION, AND RECOVERING THE HYDROGEN PRODUCED. 